<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>css处理</title>
  <script type="text/javascript" src="../js/jquery-3.4.1.min.js"></script>
<style>
  div{
    width: 100px;
    height: 100px;
    background-color: red;
  }
  .c1{
    width: 200px;
    height: 200px;
    background-color: green;
    /*切角成圆*/
    border-radius: 50%;
  }
</style>
<!--  触发后才会执行-->
  <script>
    $(function (){
    $("div").mouseover(function (){
      // className
      // $(this).addClass("c1");
      // 行内式,style
      // css(样式名):获取指定样式的值
      // css(样式名,样式值):设置css样式
      $(this).css("width","200px")
      $(this).css("height","200px")
      $(this).css("background-color","green")
      $(this).css("border-radius","50%")
    });
      $("div").mouseout(function(){
        // $(this).removeClass("c1");
        $(this).css("width","100px")
        $(this).css("height","100px")
        $(this).css("background-color","red")
        $(this).css("border-radius","0%")
      });
    })
  </script>
</head>
<body>
<div></div>
</body>
</html>